Beside and Besides are commonly confused words. Not surprising, since only an 's' separates the two words. However, both words have different meanings and have different contexts of usage.
Beside is a preposition.
Meanings: next to; at the side of; alongside; by; near; nearby; close; adjacent to.
Besides is an adverb.
Meanings: as well; in addition; also; above and beyond; moreover; what's more; what's more; further; anyway; likewise.
Examples of Beside:
1. The old man sat beside the young girl on the garden bench and he too started throwing grain to the pigeons pecking at her feet.
2. When the bus stopped next to Kunal's car at the signal, he was worried as it was too close to his car.
3. The shopkeeper gave accurate directions to the tourist to locate the bus depot and told him it was beside the Mysore Palace.
Examples of Besides:
1. The tour guide gave the group basic first aid training besides giving them instructions on what to wear for the rock climbing expedition.
2. At the board meeting the young executive explained the manner in which the new product would be launched besides giving the company officials an idea of the target group through a visual presentation.
3. Besides buying a bunch of grapes, Saraswati decided to buy the box of strawberries too.