Better explanation

Question

I wish it was better explained when to use this tense instead of just giving examples

Accepted Answer

Hey Alesha, remember how we use the verb "hay" to say "there is" or "there are"?  For example, we could say:
Hay un buen sistema educativo aquí. (There is a good educational system here).
But what happens if we put an opinion phrase in front of this?  Then we have to change "hay" to the subjunctive form "haya".
No opino que haya un buen sistema educativo aquí. (I don't think that there is a good educational system here.)
If you check the examples you'll see that they can all be expressed in this way, even though some are translated differently into English.

Answer

Hola Alesha
Unfortunately it would be impossible to have an individual lesson for each verb in each tense explaining their uses in all of them.
The lesson you came across is about learning how to conjugate, about "form" not "usage", so there aren't explanations about all the possible uses of that verb/tense, only about the formation/endings.
If you'd like to learn more about usage, for example, uses of the "present subjunctive", I recommend that you do a search from your dashboard (next to your photo and flag on the right top corner) and type: present subjunctive; You will see lots of lessons related to that tense and then you can navigate through them to learn about usage. 
I'll give you some links to start with:
esperar que + present subjunctive (to hope)
ojalá + present subjunctive (to hope)
negative opinion phrases with subjunctive 
querer que + present subjunctive
I hope it helps.
Saludos cordiales