Sum of Countifs: a simple question, I'm sure

I am trying to count the number of times a string appears in a column. Cells in that column have that string, and occasionally other data as well. I'm not sure why this isn't working for me:

=SUM(COUNTIF(Sheet2!G:G,{"Things"}))

This next formula is working for me, but only counts the string if it is the only thing in the cell.

=COUNTIF(Sheet2!G:G,"Things")

What formula should I use when I want to count a string whether it is the only thing in the cell or not? Thank you for any help you can offer, in advance.