John provided great links for you to review...
The short answer is yes...you can use your own printer for many things. You can use it for inkjet heat transfers such as JetPro SoftStretch (JPSS) for white garments or opaque heat transfers such as Ironall for Darks or JetWear. You can also use your own printer for doing dye sublimation which is used for such things as mugs and other "hard" goods. You can also use it for 100% polyester garments or 100% polyester coated garments (SoftLink by Hanes). However, it is not recommended that you use the same printer for doing both as there will be a residual amount of the ink left in the printhead when changing cartridges. Not to say it is impossible (I've done it in a pinch) but not recommended.
Oh, pigmented ink is recommended for most heat transfers. However, the new Claria (water resistant) ink has been working well with the JPSS transfer paper.
Of course, this only touches on what you can do with a "printer" and does not address the many other methods available (DTG, screenprinting, & vinyl) but there is much info on this forum about all of them.
My recommendation is to read until your eyes bleed!! LOL But don't be afraid to ask questions. There are alot of great and very helpful people here.
Good luck!!
John