The simplest way to explain blockchain is that it is a peer to peer transaction using a ledger that is attached to the transaction and can't be removed.
To understand it better, let's use the example of a train. When a transaction occurs it is like adding a train car to a steam engine. The steam engine hypothetically has four numbers stamped on its engine. Say you buy a share of Litecoin or Bitcoin. When you buy the share, the transaction runs through a series of numbers. The numbers would include the four numbers stamped on the steam engine, and then a new set of numbers stamped onto the car your transaction just added to the steam engine. Then I go to buy some litecoin or bitcoin. The blockchain transaction means I will get a series of numbers that included the four numbers on the steam engine, the four numbers on your train car, and then my transaction includes four new numbers on my train car.
Each train car has the capacity to hold things if you are using a crypto currency like ethereum. So maybe my transaction includes putting a house title in my train car or a stock in my train car.
This blockchain technology makes it harder for hackers because they have to know the steem engine number and the number on each train car or transaction. Therefore blockchain technology becomes a more secure and trusted way to do a transaction. The train cannot be easily separated from the cars, so the transaction becomes more reliable and secure.