To understand a concept is to be able to articulate it.
If you understand how progressivism is allegedly different from communism, you will be able to state it in one sentence.
A communist will just steal your property. A progressive prefers to regulate it.
Phase two is that the communist kills you if you resist his schemes of nationalization. That's government property, not yours. A progressive, on the contrary, will harass you more, regulate you more, increase your taxes, more fees, increase bureaucracy, audit you with the IRS, show up at your brother/uncle/sister's small business and conduct "compliance reviews", smear you using their journalist friends, etc. This is exactly what they've done over the last 100 years.
That's primarily only regarding property though. But, I have a feeling you will not accept that single sentence answer. And yes I can back this up, see Stuart Chase's 18 points, most notably #17:
Not much "taking over" of property or industries in the old socialistic sense.
Stuart Chase was only an adviser to Franklin Delano Roosevelt and he was the guy who actually coined the phrase "New Deal".
That's 13 words in my single sentence answer above, if we are counting. Ironically enough, Chase's was also 13 words. How short of a sentence were you looking for and in what context?
In the end though, your explanation taught me something I didn’t know before.