I am trying to combine two columns of information in excel but the concatenate function doesnt seem to work for it. It may just be my ineptitude in excel but I just cant seem to figure this out.

I have 3 colums

Column A__________Column B___________Column C
tree_______________ .jpg
dog________________.gif
House______________.png

But I cant seem to be able to make it so that column C has tree.jpg and dog.gif and house.png

Is concatenate the wrong thing to use here? or am I making my formulas incorrectly?