It's important to keep the grammatical relations (or syntactic functions) separate from the parts of speech.
- Smiling is good for you.
- I love to see your smiling face
- Joe ran from Melissa, smiling as he went.
- She was grinning, smiling even, as she walked up to the podium.
- Look at those two smiling over there!
The probable reading is that smiling is a gerund-participle verb in each example in 1-5 above. However, the grammatical relations in each sentence are different. In those sentences where the grammatical relations are those we associate with nouns, traditional grammar would call them gerunds. In all other instances, where they head clauses functioning as Modifiers of some description, traditional grammar calls them participles. In many modern grammars they are just recognised as the -ing forms of verbs which can do different jobs in a sentence or phrase. We call these gerund-participles. They head gerund-participle clauses. I'll call these clauses GP's for short
In (1) the GP is Subject of the sentence. In (2) the GP is the modifier of a noun (the same kind of job that adjectives and nouns can both do as well). In (3) it is an Adjunct, more specifically a Predicative Adjunct describing the Subject, Joe. In (4) the GP is part of a co-ordination (it means something similar to the coordination in she was [grinning and smiling]) which is functioning as Complement of the verb BE. In (5) the GP is post-modifying the word two, in the same way that an adjective phrase or relative clause might.
Remember that even though many of these functions (Subject, Modifier and so on) are functions that may be done by noun phrases or adjectives, this does not make the verbs doing these jobs nouns or adjectives. They are verbs! Specifically, they are gerund-participle forms of the verb.