Does it really matter if I connect two or more Internet connections (from different ISPs or sources) simultaneously? Do all of these speeds add up? or Ubuntu just sticks with one connection and others just kept connected doing nothing? Is it possible I can make all the Internet connections added up and have a faster Internet? Obviously the speeds won't add up but load can be shared. Can I do this?
Bonding, also called port trunking or link aggregation means combining several network interfaces (NICs) to a single link, providing either high-availability, load-balancing, maximum throughput, or a combination of these. See UbuntuBonding.