These are the mechanisms which carries your fluid through your hydraulic system. You might notice this by your brake feeling “hard” when you depress it. You may pull to one side or you may get something of a “spongy” pushback fromthe system. You should have this looked into straight away.
If you are mechanically adept you may wish to check in on some of these issues yourself. However if you don’t know what you’re doing you can often cause more harm than good, so be careful. Your brakes are the only thing standing between you, your speeding engine, and the solid rock wall which lies ahead of you.