An aisle is, quite simply, a passageway, and can refer to a passageway or corridor in a number of places.
Everyone has to be familiar with the phrase 'walking down the aisle', which is synonymous with 'getting married'; the aisle is the passageway between the pews down which the bride walks from the door of the church to the altar where her husband-to-be is waiting.
The other common usage is in a supermarket or warehouse, where the aisle separates the rows of shelving that carry goods (although shoppers sometimes appear to misuse 'aisle' to refer to the shelving, for example when goods are shelved 'at the end of the aisle').
"I'll just check out the end of this aisle," Blair said. "I think the eggs have been moved to there."
Jim sighed. "I wish they wouldn't move things around so much," he grumbled. "Makes it difficult to find what you want."
In a theatrical setting, people are sometimes said to be 'rolling in the aisles' - i.e. the passages leading to the seats - during the course of a comedy production. This is, of course, purely metaphorical, but people reading in a review that the audience was 'rolling in the aisles' understand that the production is very funny.
An isle is a small - or sometimes not so small - island. Many of the UK's islands are known as 'The Isle of X' - e.g. Wight, Man, Mull, Skye - and some of them are fairly large. Indeed, another name for the UK is 'The British Isles', though that's not used much now because the Republic of Ireland is a totally independent country - although it and Northern Ireland together are often called 'the Emerald Isle'.
"Why call it 'Isle of Skye'?" Jim asked as he checked the map of the area Blair had suggested for a holiday. "Wouldn't 'Skye Island' be just as good?"
"You'd think so, wouldn't you? But as soon as one of those islands gets a name, its status seems to change to 'Isle of X' or if there's a group of islands, 'X Isles'. Custom."
Jim simply shook his head in bewilderment.
It's quite simple, really. If it's a passageway, it's an aisle. If it's surrounded by water, it's an isle - short for 'island'. And the similarly sounding 'I'll' just means 'I will'.
Source - The Free Dictionary