20:2And he laid hold of the dragon, the serpent of old, who is the devil and Satan, and bound him for a thousand years,

And he LAID HOLD of

The 'he' refers to the angel coming down from heaven in the previous verse. We have one angel LAYING HOLD of another angel. That the devil can be captured indicates that he is finite and not omnipresent, even though we sometimes feel that is not the case.

Symbolically, this indicates that evil, even as the devil is the embodiment of all evil, can be corralled; but it isn't easy. Humanly, we couldn't have LAID HOLD of the devil; thankfully it is Christ who strengthens and establishes us. It is Christ and his angel(s) who do that for us (1 Peter 5:6-11).

the DRAGON
bestial nature
Revelation 12:3-17; Revelation 13:1-4; Revelation 16:13
the SERPENT of old, who is
cunning introducer of sin
into the earth
Genesis 3:1-6; 2 Corinthians 11:1-6
the DEVIL and
slander or malicious gossip
2 Timothy 3:1-9; Titus 2:1-10
SATAN,
adversary and accuser
Revelation 12:10; John 8:31-44-59

There is no doubt whom the angel LAID HOLD of. These four names also are used in Revelation 12:9.

and BOUND him for a THOUSAND YEARS,

The angel uses the GREAT CHAIN (previous verse) to BIND the devil. The relevance of this is that the DRAGON, the SERPENT of old, who is the DEVIL and SATAN is going to be controlled and restricted in the abyss (next verse). No more will he be able to prowl around the earth trying to deceive humans.

There is much discussion in commentaries whether the THOUSAND YEARS means a 1,000 years or just a long period of time. Considering how precisely time is given elsewhere in the Revelation (for example Revelation 8:1; Revelation 9:5; Revelation 11:3; Revelation 11:11 and so on), and that this exact time is used six times in verses 2-7 of this chapter, indicates this is a literal THOUSAND YEARS. Now having stated that, given all that has happened to the earth and solar system (Revelation 8:12 and Revelation 16:17-20), time may not be measured as now. That is, day lengths may be altered. We will just have to wait and see.