Well ideally, securities are equity interest in an enterprise. Or in other words shares of a company. By holding these securities you expect to gain from the gains of the company (in the form of dividends-mostly). Think of it as being a partner in the company.
On the other hand, a token can just be a means of exchange. So for example - sports cards that are exchanged by teenagers are sort of tokens. The cards themselves dont hold any intrinsic value except that the holder values them. By exchanging these cards you don't really participate in a company's performance.
What a lot of ICOs do is this - they put an entry barrier to their system and argue that you need to use these "sports cards(tokens)" to use their services. At least that's how they try to structure it legally and there is nothing wrong with it.
I am not sure if this explanation helps. I tried to be non-technical.
The easiest example I've found that works is Arcade Tokens: you go to an Arcade, you have to buy tokens to use the machines, you can't use those tokens for buying pizza around the corner- they have defined utility. You also don't get a share of the revenue made by the Arcade by owning their tokens. If you gain speculative value from owning those tokens or can use them for anything beyond a defined utility- it's a security.