What size is Ram and Hard drive of the new Mac? And what does SSD mean?

If the question is specifically about the current 12-inch MacBook, it’s a standard 8 GB RAM and 256 GB solid-state drive. It’s by definition not a hard drive. One can be configured for 16 GB RAM and/or a 512 GB SSD. These are fixed and can’t be upgraded for the new models.

MacBook - Technical Specifications - Apple

SSD = solid state drive. Instead of a drive with a spinning disk it uses technology similar to that in a USB thumb drive. Less energy consumption, faster, quieter. More costly.