Stress is something that unfortunately isn’t frequently taught in the classroom, but makes all the difference when you want to make yourself understood and you want to understand the underlying meaning that is being conveyed to you. Not many english-language learners realize, but by the way we stress a word we alter the meaning of the sentence.
To stress a word is to:
1) Make it sound louder
2) Use a different pitch for the word
I had pizza last night. (by stressing «pizza» you mean that you had «pizza» instead of what you normally eat)
I had pizza last night. (by stressing «last» you mean that you «already had pizza and probably don’t want it again)
If you are a language learner of any level you should try incorporating these speech patterns into your sentence structure. Try it and you’ll quickly see how your language level improves.