Reading a written pattern
A crochet pattern is a compressed program, and the notation varies by era and country. The survival kit:
Modern US amigurumi style
R4: (3 sc, inc) x 6 [30]
Round 4: repeat the group "3 single crochet, then an increase" six times;
the bracket is the stitch count you should end with. That trailing count is
gold: it is the check that catches mistakes one round after you make them.
The US/UK trap
The SAME words name DIFFERENT stitches. UK "double crochet" is US single crochet; UK "treble" is US double. If a pattern says "dc" and the fabric is coming out twice as tall as the photo, you have a UK pattern.
Antique patterns (1840s to 1920s)
No stitch counts, sentences instead of shorthand, and their own vocabulary: "Sg. C." (sc), "D. C." (dc, mostly), "plain" (sc), "widen" (increase), "narrow" (decrease), "miss" (skip). They trust you to keep count; a modern reader should write the counts in the margin, round by round.
Repeats
Asterisks, parentheses and brackets all mark repeats: "* ch 5, sc in next, repeat from * around" and "(ch 5, sc) around" are the same instruction.