Most of the time a Mac application is nothing more than a folder (called something like MyApplication.app) that contains all the program files but which appears to the user to be a single file. When you run an application most will generate user preference files that are stored under your user account (usually in the /Users/YourName/Library/Preferences folder or elsewhere in the /Users/YourName/Library folder) but by and large all the files for the application are stored in the applications folder. Given this you can uninstall most applications by simply dragging the application's icon from the /Applications folder to the Trash.
There are exceptions to this. Don't attempt to uninstall Apple's own applications (such as iLife apps or things like TextEdit) else that usually ends in tears later and some applications that install things like kernel extensions (for example, a Virtual Private Networking application like Cisco VPN) often need an uninstaller to be run. By usually uninstalling is just Drag-n-Drop to the Trash.
Applications like AppZapper help clean up the preference files created but given that these are often only a few KB in size, leaving them lying around won't cause any issues like slowing down your system.
EDIT: Just a word to the wise but it's best to call a Macintosh computer a "Mac" rather than "MAC". Some people get a little pissy about this but it's also worth remembering that MAC also stands for "Media Access Control" in networking and given that this can be a factor in problems it saves confusion.