what's TOEFL?

we often heard about tofel,but many quetions come to my mind:

is a certeficate? or just to know our english level?
who is really the supervisor? persons? universities?
people who have tofel in different country,have they the same english level?

is it for leaners or teachers?

are exersices of vocabulary,grammar,listening…etc the same seeing we find thousands
of web sites provide us with their pop up window to study tofel,

where i go then and if it is a certteficate where can i get it? free or paid? what about its international value? is it personal, i mean it only makes us satisfied and just to test our level.
thanks to everyone will understand me and give help.

TOEFL listening lectures: How do botanists define a seed?

I’m sure many of the learners here will fill you in on the advantages (and any disadvantages) but in the meantime, you can find useful information here.
If you have a problem understanding th webpage then please ask again.