1. means "especially" and is used to modify adjectives or adverbs to emphasize the degree. Sometimes it also modifies verbs.

2. Used to emphasize the purpose, meaning "specially" and "specially", usually used with infinitive or preposition for phrase.

3. After stating a fact, list a representative example for further emphasis, which can be followed by nouns, prepositional phrases, clauses, etc.

It is very cold in winter, especially in Beijing in winter it is very cold and especially in Beijing.