Most of the time, when we say stuff we mean things. For example: "I left all of my stuff in my car" - I left all of my things/possessions in my car. This word is used both in American and British English. Here are some other common expressions using stuff:
"I've got some stuff to do at home." Meaning: I have work that I have to do at home. (Probably housework).
"The new guy in my office is hot stuff." Meaning: The new guy is sexually attractive."
"Don't sweat the small stuff." Meaning: Don't worry about issues that are not important. (More common in American English).
"Her life was the stuff of legends." Meaning: She had an amazing life. The kind of life that you read about in books or see in films.
"Ask Julia to explain it to you. She really knows her stuff." Meaning: She has a lot of knowledge/skill about a topic.
"I cleaned my room because my mum said there was stuff everywhere." Meaning: There were things everywhere - it was untidy/messy.
Fill: "I just about had enough time to stuff some clothes into my bag and then leave."
Eat a lot: "I stuffed myself with pizza last night while watching a movie."
"I felt stuffed after eating too much for lunch."
Here's an American comedian talking about stuff. Watch it if you want to, it's not important!
Link: Do you speak British English? Words you need to know!
