Rosetta, the application you never knew you had, is gone starting with Mac OS X 10.7 (Lion, Mountain Lion, Mavericks, and Yosemite all lack it).
It is not in any shape or form related to the language translation teaching tool by the same name.
It is the background program that lets Intel Macs run applications written for Mac OS X at a time
when PowerPC Macs were the only thing around (before 2006). It is no longer there to enable their ability to run when you upgrade to the newer systems.
It also means that programs with older installer programs may need updating as well, so verify the system requirements do not lack
Mac OS X 10.7 or later, or drag their installer program into the Applications folder to verify they aren't for PowerPC only. You'll see later how
to determine that with the System Profiler program.
Go to Apple menu -> About This Mac to determine exactly what you have. Alternatively:
See https://discussions.apple.com/docs/DOC-6413 to identify your Mac.
See https://discussions.apple.com/docs/DOC-2295 if migrating data from a PowerPC Mac to an Intel Mac.
G3 without USB is maxed at 10.2.8, except for the Powerbook G3 250 original Powerbook G3 (also known as Kanga), which could only
be updated to Mac OS 9.1 (not to be confused with Mac OS X 10.9.1, which is 13 years newer).
G3 without Firewire, but with USB are maxed at 10.3.9, except the Powerbook G3 Lombard (Bronze Keyboard) which may have CPU specific issues that limit
its upgradeability at all.
G3 or G4 of 800 Mhz or less with Firewire are maxed at 10.4.11.
PowerPC Macs G4 867 Mhz (on single processor) and above (1 Ghz or higher included), and G5s can upgrade only to Mac OS X 10.5.8, and only support for syncing with iOS 5.x devices and earlier.
Intel CoreSolo and Intel CoreDuo can upgrade only to Mac OS X 10.6.8 if they have at least 1 GB of RAM (768 MB is less). This does offer for anyone in the position compatibility with PowerPC applications that don't require drivers, and the latest Adobe Flash support as of May 14, 2014, and support for syncing with iOS 7 devices.
Intel Core2Duo and XEON and later (Core i3, i5, i7 are all later models) may be able to go 10.4.4 to 10.6 to 10.6.8 to 10.9 to 10.9.2 (skipping 10.5 to 10.5.8 altogether, and 10.7 to 10.8.5 altogether), as will later be explained. 10.6.8 may also be upgraded directly to 10.10. However, due to Rosetta's lack of existence in 10.7 and later, this type of upgrade, and any such upgrade that does not skip the aforementioned operating systems needs to be planned carefully. This tip explains what is needed to approach such upgrade pattern once it reaches 10.7 or later.
It does mean your data if it was in Appleworks, or an older version of Quicken may
need to go through several conversion steps before you can upgrade to a newer Mac OS X.
It does mean that some newer Macs than July 19, 2011 will be faced with difficulty when approaching older applications. That date is later for some Mac models that did not receive a hardware revision until a later date than July 20, 2011, and that will also be explained later.
Some things you get with 10.7 and higher, specifically 10.7.3 and higher, are better compatibility with Java for websites from http://www.java.com/
If your machine is limited to 10.7, stick with 10.7.3 unless you require other compatibility that is only on 10.7.4 or 10.7.5. Those with 10.6.8 or earlier running Java should read this tip:
Adobe Flash compatibility with older Macs is discussed here, though if you can run at least 10.6.8, you can run the latest Flash:
Now this doesn't mean you can't upgrade to 10.7 or later, if you have those older applications, but the workarounds aren't easy,
as this tip on virtualizing 10.6 server on 10.7 or later demonstrates. Applications that aren't on this link as 10.7 or later compatible, may only work with the workaround. Alternatively a second hard drive with 10.6.8 or earlier, or second partition (which may require an erase of your hard drive)* with 10.6.8 or earlier if supported by the Mac will enable you to continue to use Rosetta. Mac models whose hardware changed (by Apple delivering a new set of hardware to stores) as of July 20, 2011 or later though have to deal with the first work around as their only choice.
The System Profiler application lets you quickly determine if you have PowerPC applications (click on image to enlarge):
Note the triangle to the left of Software has to be pointed down for the Applications to become visible.
Note the right hand side of the the Applications listing when selected says if you have PowerPC, Classic, Intel, or Universal.
PowerPC & Classic indicate PowerPC only. Classic indicates it only runs on a PowerPC with Mac OS 9 running in the Classic environment
Before you upgrade to 10.6, be aware of this tip.
Before you upgrade to 10.7 or later, also be aware of the info on this tip.
If everything is good, you can do the following upgrade path:
10.8 can be updated to 10.8.5 combo (free) as well.
An empty hard drive to 10.6 retail, then the above the 10.6.6 or 10.6.8 paths, or 10.7 USB Flash (no longer available) to 10.8 or 10.9.2, 10.9.3, 10.9.4, 10.9.5 from 10.9 is also possible.
Note: The only 10.4 systems that can upgrade to 10.8 through 10.10 are on this tip Are there 10.4 systems that can upgrade to 10.8 or 10.9?
The only 10.5 systems that can upgrade to 10.8 through 10.10 are on this tip:
The links provided should be followed to avoid any pitfalls you may get.
Lastly, Apple lists compatible printers for 10.6 and later:
Any not listed, will have to come from the vendor directly.
Apple provides updates to the printers on that link through these links by vendor:
P.S. Users with PowerMac G3, G4, G5 reading this tip should also read the migration guide before migrating data from those machines to an Intel Mac.
* An erase of the hard drive during partitioning is usually only required when you have insufficient space. With sufficient space, partitioning can be done without erasing as described here:
under "Create new partitions on a disk." You should backup regardless.
10.7.5 has this security update: Security Update 2014-003 (Lion)
10.8.5 has this security update: Security Update 2014-003 (Mountain Lion)
Lastly, for those with Microsoft Office versions that are too old, there are these alternatives: