Linking words are used to connect ideas within sentences and paragraphs. They have several functions such as contrasting information, making comparisons, and adding information or giving reasons. Some common linking words used to add information include "and", "as well as", "also", "in addition", "too", "besides", "furthermore", and "moreover". Using linking words correctly is important to avoid changing the meaning or causing confusion, and it can help improve English proficiency by allowing for more complex expression.