Hey Melissa.

Good question. For the most part, they are basically the same thing.

The word share is used more often when it is referring to individual companies.

The word unit is used mainly when it refers to a type of managed fund. You own ‘units’ in a fund, but ‘shares’ of a company.

Another difference is the income payments from companies are called ‘dividends’. The income payments from funds are called ‘distributions’. But again, the same thing, just different terminology :)

Hope that helps.
Dave