Gerund (деепричастие) is a form of verbal adverbs, because they are always connected to the main verb, they do not change their form, but at the same time have aspect characteristics.

Gerunds, as ordinary verbs, have 2 aspects:

~ imperfective aspect (it refers to the present and is formed from the imperfective verbs)
~ perfective aspect (it refers to the past and is formed from the perfective verbs)

Use of imperfective gerunds:
To describe an action that is simultaneous to the main one, that forms the background to the action or situation.


Formation of the imperfective gerund:

~ imperfective verb of a 3rd person plural (они = they) in present without its ending (-ют; -ят) + -я

Ex. (они) встречают = встречая

~ Verbs with -авать, -ставать, -знавать endings have the following formula: infinitive without -ть + -я

~ Reflexive verbs in gerund forms have the same pattern, only after -я we add the reflexive suffix (it changes from -ся to -сь).

Ex. находятся = находясь


Exceptions:
1. быть (= to be) becomes будучи
2. verbs with -чь, -уть endings + писать (= to write), хотеть (= to want), ждать (= to wait), пить (= to drink), бежать (to run) etc. do not have form of the gerund of the imperfective aspect.

Знать:

(они) знают = > зная


Встречаться:

(они) встречаются = > встречаясь