The head (or glans) of the penis has something called a frenulum – a thin elastic band of skin underneath – similar to that found under the tongue.
The penile frenulum should stretch to allow the foreskin to comfortably slide and retract from the head of the penis when erect. If the frenulum is too short or thick it may restrict normal movement of the foreskin, a medical condition known as a Frenulum Breve. This can lead to problems during erection and sexual activity, including: penile curvature downwards, difficulty penetrating, bruising, repeated tears, bleeding and pain.