On one end is a catheter tip which is the part of the catheter that is inserted into the urethra. The catheter tip can be curved (referred to as coudé) or straight.
The funnel end on the other side helps the urine drain into a toilet or receptacle and it also enables you to attach a drainage bag. The funnel ends can help indicate the size of catheter you are using. A funnel color reference chart is shown below which will help you determine which size of catheter you have.
Catheters are sized by French size and abbreviated fr. Typical French sizes range from 5 fr - 20 fr. Your health professional will let you know which size of catheter is best for you.