A Raycast checks whether an invisible ray hits something.

if (Physics.Raycast(
    transform.position,
    transform.forward,
    out RaycastHit hit,
    5f,
    layerMask))
{
    Debug.Log(hit.collider.name);
}

Useful hit data:

hit.point
hit.normal
hit.distance
hit.collider
hit.transform

Common uses:

• shooting
• interaction
• ground detection
• AI vision
• obstacle checks