Explaining how a name is written
Since many Chinese characters are homonyms it can be difficult to tell how a name should be written. This problem is usully overcome by people indicating how their name is written by naming one or more of the constuents that make up each character of the name.
For example:
You might hear somebody say 我叫王李， 木子李。 Wang is a common surname so there is no need to specify the character.
Li however could be written in a number of different ways. So by saying 木子李 the speaker is in fact saying 'Li like the character li with the tree constituent (木).'
Similarly, 我叫张红。弓长张， 红色的红。 Literally 'I am called Zhang Hong. Zhāng like the character comprising 弓 (gōng) and 长 (cháng) and Hong like 'hóng' in the color 'red'. In this case the first character is identified by specifying both of its constituents, the second character is clarified by pointing to its use in the word 红色 (hóngsè) red.