The document discusses linking words, which are words that connect sentences by indicating their relationship. Linking words have several functions such as contrasting information, making comparisons, adding information, or giving reasons and explanations. It is important to understand the different meanings and uses of linking words as they help improve English proficiency and allow for more complex expression. The document then provides examples of different types of linking words such as words to add information ("and", "as well as", "also"), express contrast ("but", "however", "although"), indicate reason and consequences ("so", "because"), and other examples.