neck
The word 'collo' in Italian is used to refer to the neck, which is the part of the body that connects the head to the rest of the body. It is used in the same way as in English, for example, 'He has a sore neck' would translate to 'Ha un collo dolorante' in Italian.
My dog has a long neck.
This phrase is used to state a physical attribute of a subject, in this case, a dog (il mio cane) is the subject and has a long neck (un collo lungo).
My neck hurts.
In this phrase, the speaker is expressing a physical discomfort that they are experiencing. Here, the subject (il collo or 'the neck') is what is causing the discomfort (mi fa male or 'hurts me').
Wear a scarf around your neck.
This sentence is an example of a command or an instruction. The speaker is telling someone else to put (indossa) a scarf (una sciarpa) around their neck (al collo).