[Kushan]

That's essentially it, you've got two completely separate connections, with two independent IP addresses coming in. Your load balancer will just switch between each one every time you create a new connection (Which means every time you click a link on a site or download a file or open up an application or game). So no single connection can go faster than the fastest single line, you only benefit from downloading multiple things at once.

Load balancing isn't perfect, either, some sites and services will refuse to work with it and depending on how you do it, you might not get an even 50/50 split all the time.