a) He loves painting.
b) He is painting.
Both of the sentences above are different. (a). /He loves painting/ is built from gerund and (b) /He is painting/ is built from participle or present participle.
GerundBasically, gerund is a verb. But when it is in a certain structure, it becomes a noun. How could that be like that? It is because gerund does not indicate that someone or a thing is doing an activity or to do something physically. It means that gerund is the way to express something or to give a tell or to inform someone about one's activity (both habitual actions and daily activities).
Mostly gerund is positioned in a context which the point of the information is served to someone.
I like smoking.
Waiting is boring.
My hobby is swimming.
Note that, /boring/ in the sentence above is a noun which is derived from the adjective /bored/. So, bored is not a verb and that is different of gerund which is derived from a verb or infinitive.
Present ParticiplesWhen physical activity can be seen right now or something is being done physically, the present participle (which indicates the point of current action) must be used.
He is cooking.
She is doing her assignment right now.
They were talking the lessons.
In the example above, /cooking/, /doing/ and /talking/ position themselves as an activity or work which are being done physically.
Therefore, present participle can be seen in the pattern of Continuous or Progressive Tense. That means that Present participle can be an element of Continuous or Progressive Tense.