It sounds like you just updated to Catalina or Big Sur. iPhoto no longer runs on those OS' because they are 64 bit only.
You can use Photos - iPhoto's replacement - with your iPhoto Library. Launch Photos with the option key held down. from the resulting dialog, choose your iPhoto Library. Photos will create a new library from your iPhoto media. Your iPhoto Library will not be changed, though it will be renamed.
You can certainly trash the iPhoto application, though it does not take up much space. Once you have converted the iPhoto Library to Photos, and you have verified that your images are in the new library, you can remove your iPhoto Library.