An aisle is a long, narrow space between rows of a seat in an aircraft, church, theater, auditorium, or in between rows of shelves in a store. Aisle and isle may sound similar but again, they are two different words. 

For example:

All heads turned as the bride began walking down the aisle.

I prefer the aisle seat over the window seat when I fly.

Coffee and tea are in the next aisle.

The musical had actors dancing in the aisles.

Besides, an aisle can be more than a passageway between seats. Supermarkets have aisles, factories have aisles, warehouses have aisles, etc.

In a political context, aisle refers to a situation when members of one political party talk about working with members of the opposing party. They often speak about their reaching across the aisle.

For example:

In the USA, they often refer to the Republicans and the Democrats as “the two sides of the aisle.”

We need to reach across the aisle to fix this problem.

The metaphorical use of the word refers to the ways parties arrange themselves in meetings of Congress or Parliament, with certain parties sitting on certain sides of the aisle. Because of this segmentation, political opinions or public policies became known as coming from “one side of the aisle or another.”

P.S. When you see people using isle in a political context, it is a mistake. The correct word choice is the aisle.