This is a term that you will often come across when purchasing your hiking light and is a basic unit for measuring brightness, just as the gram is a basic unit for measuring weight. Lumen is related to the word luminous, which means ‘bright’ or ‘radiant’. A typical light bulb in your home might produce about 1000 lumens.
When hiking, there is no correct amount of lumens to use however one of my favoured headlights, the Petzl E+lite has a strength of 50 lumens while the Petzl Swift RL Headlamp has around 900 Lumens. Anything less than this is not going to be to helpful at night-time
Close up of Petzl E+lite