wood
The word 'legno' is the Italian translation for the English word 'wood'. In Italian, 'legno' is used to refer to the material that trees are made of, as well as to objects made from this material, such as furniture or tools. It is also used in phrases such as 'fare di legno', which means 'to make of wood', or 'essere di legno', which means 'to be made of wood'.
You need to cut the wood for the fireplace.
This sentence is a command, instructing someone to cut wood for the fireplace. 'Tagliare' is the verb 'to cut', 'il legno' is 'the wood' and 'per il camino' means 'for the fireplace'.
Those trees are a good source of wood.
This sentence is talking about trees as a source of wood. 'Quegli alberi' means 'those trees', 'sono' is the verb 'are', 'una buona fonte' means 'a good source' and 'di legno' indicates the type of source, which is wood in this instance.