...so can you install Linux programs/tar.gz on BSD?
This is a question with a complex answer that would probably only confuse you as a new user. The short answer is "Maybe, but don't bother."

In *nix Land your first stop should
not be a project's homepage, but the official software repository for your operating system. On FreeBSD, this means your local ports tree (for building custom packages from source code) or the official package repository (for quickly installing pre-built packages with reasonable default features/options). Follow the resources others here have mentioned---the relevant sections of the
Handbook can teach you the basics---and check out the
ports(7) and
pkg(8) manuals when you get a chance. Since you're new, I'd recommend starting with pre-built packages to get up and running quickly. You'll probably hear a lot of buzz about two (fantastic) programs called Poudriere and Synth, but hold off on those for now.
The folks in the Arch Linux community have compiled a pretty good list of
commonly used applications, organized by purpose and interface type (GUI vs. CLI/TUI). From my experience, if it's on that list, it's almost certainly available on FreeBSD. You can have a look at that list, and search for anything that interests you using
pkg-search(8) or FreshPorts. A neat tip: if you use DuckDuckGo as your search engine, you can do a quick search of FreshPorts with its "!bang" syntax---for example,
firefox !freshports
.
