The Mishnah before us describes in detail how the process unfolded in which tens of thousands of Jews slaughtered the Pesach offering on erev Pesach. The Mishnah establishes that the Pesach was slaughtered in three groups, and it derives this from the wording of the verse, which states that the offering must be slaughtered by "kol kehal adas Yisrael" - the entire assembly of the congregation of Israel.
The source for dividing into three groups:
Klal Yisrael is described in this verse with three terms:
"kehal" - assembly
"adas" - congregation
"Yisrael" - Israel
From these three terms we learn that the slaughtering was done in three separate groups.
The procedure of the first group:
The first group entered the Azarah in the Beis HaMikdash, and the Azarah filled up with people and with their Pesach offerings. Once it was full, the doors of the Azarah were closed, and the kohanim sounded their trumpets: tekiah, teruah and tekiah. The kohanim stood arranged in rows and columns, from the place where the slaughtering was done all the way to the mizbeach.
The rows of kohanim and the vessels in their hands:
The kohanim held vessels for receiving the blood, made either of silver or of gold. The rows were uniform:
One row of kohanim in which everyone held silver vessels.
Another row in which everyone held gold vessels.
Silver vessels and gold vessels were not mixed together in the same row, both because uniformity was desired and because it looked more attractive that way.
Why the vessels had no flat base:
The vessels designated for receiving the blood were not made with a flat base, but with a pointed one. The reason: one of the kohanim might set a vessel down on the floor, and with thousands of blood vessels in use the blood was liable to congeal, and then it could no longer be thrown on the mizbeach to fulfill the Pesach offering with it. Once the base was made pointed, the vessel could not be set down at all, and the kohanim were forced to keep passing it from hand to hand until the blood was thrown on the mizbeach.
In summary: In this Mishnah we learned about the division of those slaughtering the Pesach into three groups, derived from the wording of the verse "kol kehal adas Yisrael"; about the procedure of the first group entering the Azarah, the closing of the doors and the kohanim sounding the trumpets; about the uniform rows of kohanim holding silver vessels and gold vessels; and about the pointed base of the vessels, designed to prevent them from being set down and to prevent the blood inside them from congealing.