Why Do Some Soldiers Hate The National Guard?

I'm about 3 years new to America so I'm still figuring out how things work. I've seen jokes in movies and TV shows where USA Soldiers make fun of National Guard. For example in the tv show that 70s show Red who's a Vet makes fun of national guard and said they get to live in Uncle Same house while soldiers don't and that they drink girly drinks. I've also seen stuff online where soldiers or marines call National guards cowards or manipulators or opportunist, and I saw someone online who said they served and they said it pisses him off that the average citizens doesn't know the difference of sacrifice a solider and national guard makes and they praise soldiers and nations guard as if they are in the same level but aren't and that national guards shouldn't be praised as such?

I'm not even sure exactly what a National Guard is and why some soldiers hate National Guard. Or why some National Guard hate soldiers.

I'm confused about this, can someone explain this to me? Thank you
Why Do Some Soldiers Hate The National Guard?
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