The cache on your MacBook Pro is a trove of temporary Internet files, cookies and form data that your computer stores in order to speed up communication with websites. While the cache plays an important role for your Macbook's browser, it can quickly fill up, causing your browser to lag. Empty the cache on your MacBook Pro to delete any cookies and temporary Internet files saved on your computer.
Click the "Safari" icon on the Dock or in the "Applications" folder to open a Safari browsing window.
Click the "Safari" button on the menu bar.
Click the "Empty Cache" entry in the menu that appears to clear the cache off of your MacBook Pro.