The noun memorabilia describes items that remind you of a certain event or time period. Parents who save every drawing and report card their children bring home are collecting memorabilia for the future.
Been there, done that, got the t-shirt? That t-shirt is memorabilia. Memorabilia refers to anything that commemorates an event. It shows you were there — you have the t-shirt to prove it. But t-shirts didn't even exist in 1806, the year memorabilia was coined from the Latin word memorare, meaning "to bring to mind." You save memorabilia to help you remember, or jog your memory.