"Corren" and "corriendo" - why the verb is changing?
Hola!
I have two pictures - the horses are running and one horse which is standing. And two descriptions:
"Caballos corren"; "el caballo no esta corriendo".
Other example - "gatos duermen", "el gato no esta durmiendo".

What does this change mean? My translator doesn't know these words "corriendo", "durmiendo" etc.:(

Question

"Corren" and "corriendo" - why the verb is changing?
Hola!
I have two pictures - the horses are running and one horse which is standing. And two descriptions:
"Caballos corren"; "el caballo no esta corriendo". 
Other example - "gatos duermen", "el gato no esta durmiendo".

What does this change mean? My translator doesn't know these words "corriendo", "durmiendo" etc.:(

Answer

-endo and -ando is like -ing. They are the gerund of the verb.
Corriendo= walking
Durmiendo= sleeping

Answer

The horses are running (Los caballos están corriendo) is the present continuous but when you say The horses runs (Los caballos corren) is the simple present. 
Los caballos estan corriendo = it's something that's happening continuously
Los caballos corren = An action that happens but it doesn't continue. 
That's the difference! Actually it's not a different meaning

Answer

This is the difference between the present tense and the present progressive tense. It's similar to English's grammar: I run, I am running. The later is the present progressive and emphasizes the action is happening.

I don't want to oversimplify it so I would google "Spanish present vs present progressive". Good luck :)

Answer

Horses run. Cats sleep. Humans eat both horses and cats.

Answer

the words "corriendo" and "durmiendo" are also called gerunds. The -iendo ending is for er/ir verbs while -ando is for ar verbs.

Ex: Estoy caminando. I am walking.