Hi Helen,
I think 'term' is a word for a period of time. In my university, we had two "semesters" each year- the Fall semester started in August and finished in December, and the Spring semester started in January and finished in April or May. (We also had a summer semester)
I think you can use both words, but in the United States, I think the word "semester" is more common.
I hope that helps!