"Important" is an adjective while "importantly" is an adverb. In the sentence, "It is more important for us to give than to receive," the word "important" is an adjective describing the subject "it." In the sentence, "More importantly, we can share the information with all of you," the word "importantly" is an adverb describing the verb phrase "can share." Most adjectives (but not all) can be turned into adverbs by adding "-ly" to the end of the word. Adverbs describe verbs, adjectives, or other adverbs; while adjectives describe nouns or pronouns. Hope this helps! Let me know if you could use more explanation.