Pepper Potts first appears in Iron Man played by Gwneyth Paltrow and directed by Jon Favreau. She is the assistant to Tony Stark love interest (but that comes more in the second movie). She is smart and quick witted and can take anything that Tony throws at her as ridiculous as she finds his ideas. And she is strong business woman that gets what she needs done no matter who she has to deal with.
In Iron Man 2 she is still a big part of Tony's help behind the scenes while he's Iron Man and in his company, which she is now in charge of.
She makes a small appearnece in The Avengers. Here she helps Tony gather info on his fellow avengers.
Iron Man 3 is where she gets her biggest role. She is kidnapped my the baddie and turned into a kind of super soldier but with a nuclear explosive potential. We get to see her do some cool fighting as she defeats the baddie and saves Tony. Of course they reverse the change so she doesn't explode, but it was fun while it lasted.
Pepper won't be appearing in Civil War and with there being no more Iron Man movies we probably won't be seeing her again. But, again, it was nice while it lasted. Have a great week everyone!