Is it ok to install windows on mac?

Yes, it's ok to do so.

There are two primary ways you can do it:

1) Bootcamp - Apple gives a program to easily partition and install the Windows operating system on a separate partition on your hard drive. This enables you to run it separately from macOS with full system resources available to it. You can't run it simultaneously with macOS in this fashion.

2) Virtual Machine - You can use a virtual machine program, such as VirtualBox, VMWare, Parallels Desktop, etc., but this will share resources with macOS, since it's running at the same time slowing down the over-all computing of the system since it has to support two operating systems simultaneously.

Use which one is appropriate for your needs.

As a followup to archieny's excellent response. there are some caveats:

1) Disk/SSD space

a) If your MacBook Pro has a small SSD--less than 256GB in size--you may have issues with either method. Windows works best when it has room to flex. With Bootcamp you partition your drive with Boot Camp Assistant and install Win in the new partition. You could need 100GB or more depending on what Win apps you plan to install. Skimp on space for Win and it will not run well.

b) Drive space allotted to Windows is NOT available to the Mac side.

c) Emulators/virtual machines need drive space to run Windows, too.

d) Summary: if your MBP has a 128GB SSD, I would seriously reconsider using it for Windows.

2) Memory (RAM) -- If you have the base 8GB RAM common to current Mac notebooks, that will probably be OK from Win via Boot Camp. Some virtual machine emulator options require more for decent usability, and you cannot add RAM to a modern MacBook Pro. To see the RAM installed in your MacBook Pro, do "About this Mac..." from your Apple menu at the left end of the menubar:

Here is Apple support doc for Boot Camp:

Boot Camp - Official Apple Support

and you may find surfing the Boot Camp forums useful as well:

Boot Camp - Apple Community

Yes, doing Bootcamp will allow you to utilize the full resources of your Mac. Take note of Allan Jones warning of disk-space utilization if using that method. Additionally, be aware that if you use Bootcamp you cannot access any files that are on your usual macOS partition. Vice versa, you cannot access anything on Windows while using your macOS partition as well. You can only use one or the other. The advantage of VM's is that you can do both at once, or more, but rapidly uses up system resources and slows down the computer's processing capabilities considerably.

For the last 10+ years I’ve maintained that my best Windows notebook has been a Mac. I’ve used both BootCamp and Parallels Desktop (virtualization) and there are good reasons for both. As you’ve noted, BootCamp will give you full speed and access to memory but you’ll have to carefully plan your hard drive allocation. I recommend nothing less than 40GB for Windows 10 and depending on the app(s) you intend to run that may be way too little. On my desktop I’ve allocated 60GB and the bulk of my data is on an external drive. Once you’ve partitioned the drive it is not trivial to expand or contract the BootCamp partition. Also, think carefully about your backup solution. Traditional Mac software won’t backup BootCamp though there is a program called WinClone that will back up BootCamp to a Mac drive. I use a Windows backup program for the Windows side since I already own such software. Until Apple switched to APFS I used open source Linux cloning software to clone the entire drive but for the moment that isn’t working.

60 GB is not enough. And no you can not change later without completely removing Windows and the Boot Camp partition first. Then you would have to start the Windows install process again this time allocating the space needed.

If you were to go buy a Windows computer you would not find a 60GB model so why would you think Windows would work with 60GB on your Mac? I recommend 256GB minimum for your Boot Camp partition unless you don't plan on installing any programs or doing anything but browsing and email. In that case you might get by with 128GB.

i gave win7 Numbers for Win10. A 60GB partition is the minimum and at that Win10 upgrades may require some software be uninstalled. 80GB is safer if you have a couple small applications to run. More than 120GB will begin to present challenges for the Mac side. This is one of the benefits of virtualization. With Parallels Desktop you can expand and contract the Windows drive allocation as needed because it is just a file on the Mac hard drive. You can even move it to an external drive if you have a sudden need for more space on the Mac side and if the external is fast you can run Windows from it.

If you are willing to keep multimedia files on an external drive, you can safely split the drive in half. It takes a bit of discipline to keep a 128GB PC or Mac ‘happy’ but the biggest part of it is resolving to keep about 10 GB free for the system to use as it will. Win10 and MacOS each require about 20 GB for system files so that’s roughly speaking giving 30GB to the system and 90GB to files and applications. Tight but doable.

But since Parallels Desktop provides a free time limited examination period I urge you to give it a try.

You are not bothering us.

You bought a 256GB Mac because 256GB met your Mac use needs. Now you want to add another operating system and I assume some programs to run in Windows. You might be able to split the drive about 125GB for each operating system. But think about why you originally bought a 256GB computer, it was because you needed 256GB. Windows users also buy 256GB or larger computers because they need that much storage. So now you are trying to install essentially 2 computers (operating systems) on a drive you originally thought necessary for 1 operating system. 128GB is not really enough for either operating system, installed apps, and created data.