I'm just a beginner of learning Spanish grammar, I bought the book Practice Makes Perfect: Completed Spanish Grammar. In the first Chapter it shows the conjugation examples for three different infinitive form endings.
comprar (to buy)
compras - you (fam.) buy
compra - he/she/it buy, you (for.) buy
usted compra - you (for. sing.) buy, are buying, do buy
nosotros compramos - we (masc., masc. & fem.) buy, are buying, do buy
What do these abbreviation in the parentheses mean? Where can I find a complete reference for it?