STD VS. STI

When you were in your sex ed classes in school, I’m sure you learned about STD’s(Sexually Transmitted Diseases). Well all of a sudden you have started hearing about STI’s(sexually transmitted infectetion). What is the difference?

STI is more politically correct, since the word disease has a negative connotation. Also the word disease makes you think that it is incurable while many STD are curable.