photoshop isnt free. There's a free trial that you can download from adobe.com that lasts for 30 days, but after that you have to pay for the software if you want to continue using it.
Photoshop comes with some brushes, but if you want more, you usually have to download them, or you can even make them yourself. [ brushes are free to download and use ]
the
big book of resources has a bunch of brush sites that you can check out if you want to look.