y - yank/copy
yy - yank the line
yw - yank a word
yW - yank a word with punctuation
y$ - yank to end of line
y^ - yanks from cursor to the 1st character of a line
yG - yanks from cursor to end of file
3yy - yanks 3 lines from the current down
y3w - yanks from cursor in current word + 2 more words to the right without punctuation
Y - yank current line only