Words, how to change sizes Options

[Amandine_Stephan...]

i have seen some ppl have big words overlapping each other, i heard it was because their font was too big?? true?? if not, how do i get my words to overlap??
And what is the code to change the font size in my entry. (ex. as if i was writing in my normal font size and i decided i wanted to write in a larger font, then go back to my normal font)