I'm trying to access a connected app through api. I created two accounts as developer account. Now, when I try to use the first account which is the account that has the "connected app" it works fine. it gets the access token and data. 

After that, I try to access the "connected app" with the other account which is developer account also. I use the "CONSUMERKEY" and "CONSUMER_SECRET" of the connected app like the other account to access it and I use the account's OWN"SECURITY_TOKEN' 

I thought at first that security token is universal also like the client_id and client_secret but it's not so I used different "SECURITY_TOKEN" for each account.

when I execute the code with the second account authentication is success but there is no data. no result. 
{
    "done": true,
    "records": [],
    "totalSize": 0
}

but in my first account there is resul. I wanted to get the data of a contact that I made for testing. but why I didn't get any result from other account???? I also put "Selected OAuth Scopes" as Full access(full). 

I also want to understand how other users access the connected app if you guys can explain please let me know. 
I am integrating salesforce to our web app so I need to know how it works. 

Thank you.!