Link Aggregation is also referred to as Port Trunking, Port Teaming, Ethernet Trunking, and Link Bundling. Cisco has a a multi-port proprietary technology known as EtherChannel. All refer to the same concept; multiple ports acting as a single connection between network devices. The key to setting up Link Aggregation between different brands is ensuring they both support the IEEE standard 802.3ad.
The value to Link Aggregation is that the two switches will treat multiple ports configured in a Link Aggregate Group (LAG) as a single trunk, providing increased total bandwidth, as well as redundancy. If two ports are configured as a single LAG between two gigabit switches, there will be two Gbps total bandwidth between the two switches (1 Gbps in each direction).