These both refer to the heathen nations. Those 'taken'
are killed, just as Noah’s flood 'took' evil men away:

Matt 24:39b-40
The flood came, and took them all away; so shall also the
coming of the Son of man be. Then shall two be in the
field; the one shall be taken, and the other left.

Those taken are taken to their deaths:

Luke 17:37
Wheresoever the body is, thither will the eagles be
gathered together.

This is a quote from Job:

Job 39:30b
Where the slain are, there is [the eagle].

Matt 24:28
Wheresoever the carcase is, there will the eagles be
gathered together.

Rev 19:21
The rest of them were killed with the sword that came out
of the mouth of the rider on the horse, and all the birds
gorged themselves on their flesh.


The ones 'left' will be surviving heathen nations that
will come to worship Jesus in the millenium:

Zech 14:16b-18
Every one that is left of all the nations which came against
Jerusalem shall even go up from year to year to worship the
King, the LORD of hosts, and... the LORD will smite the
heathen that come not up to keep the feast of tabernacles.


So we Christians are neither 'taken' nor 'left'.
We either come back with Jesus, or are raptured up to
meet Him, to receive our resurrection bodies, and then
descend with Him to rule the earth for 1000 years:

Rev 20:4b
And they lived and reigned with Christ a thousand years.

Rev 5:9b-10
You purchased men for God from every tribe and language
and people and nation. You have made them to be a kingdom
and priests to serve our God, and they will reign on
the earth.