Question about this fiber rack mount thing

I know very little about fiber, so I wanted to come here and get some help with this.

We have a couple 3rd party VPN T1 lines coming into our company. On of the vendors called and said they were going to upgrade our T1 to something like a "2.5 meg Ethernet connection". This was months ago and they gave me no details. Then the other day, a telcom company shows up to install fiber and runs a new line from the telcom poles outside all the way to out networking room.

I ended up getting pulled away all day with IT issues and they finished up and left without saying anything. I went into our networking room to check everything and saw that they had installed this in our rack. Now I am trying to figure out what this is.

I assume it is basically like a fiber patch panel that will allow more fiber connections in and out of the building, but I don't know how this works beyond that in both a technical and business sense. There is only one single white fiber line that comes into the building and connects into the back of this and so I am assuming that single line is being split up into 24 individual optic fibers. But does that mean other vendors can use this same line or is it typically limited to the company that owns it?

I guess I'm partially confused because I don't get why one company would install this for use with one single connection. We do have one other fiber connection for our primary ISP and that is a single line that connects to a little vendor-provided, 4 port Cisco switch that converts the fiber to a regular Ethernet cable..

I appreciate any help.