Yes, you can.
One of the things you get SEO points for is for having your keyword phrase in the page’s (or post’s) URL. That URL (or ‘slug’ or ‘permalink’) is created by WordPress from the page’s title – so if you have a page called ‘About’ the url will be something like ‘mydomain.com/about/’.
But what if you don’t like that url?
All you have to do is edit the page you want to change, look underneath the page title to find the permalink and then click the Edit button.
Remember, though, that if you already have a page using that url you can’t have duplicates – and that counts even if the page is in the bin (if you want to reuse the url of a binned page, either change that one to something else or empty your bin).
And WordPress is so clever that when you change your url it will automatically change any internal or menu links too – though not external ones of course.