Normally there is a duct under the public pavement. The "T" plate is an access point to the duct. Normally there will be one per house, located at the border of the public pavement and your own property. The installation crew will run a small flexible plastic pipe across your garden to connect between this T plate and the front of your house. The plastic pipe will be buried, so expect a little digging of your front garden!
At the front of your house the new cable, that gets run from the street cabinet (green box, usually), via the pavement duct and your new garden duct, is terminated in a small box - usually brown or grey. From here the another cable will be fed into your house. If you ever add other services say more TV or the extra cables needed within your house would connect back to this grey/ brown box
Edit: beaten to it
