Go into any big supplement store and you’ll see protein powders and meal replacement powders. Is the difference between the two categories largely one of branding?
Ignore names, look at ingredients.
Protein powders tend to just contain…protein and be about 100 calories per 25 gram serving and have practically no or 1g carbs, meal replacement shakes have a few more ingredients to increase calories to over 200 (for a low cal diet) but have more carbs and a lot of slim fast etc have a LOT of sugar, whereas standard protein shakes don’t have too much sugar added around 1-3grams
The main differences between the two (and as a brand that sells both meals and protein powder)
As simple as it sounds if a product says it’s a meal or meal replacement then it should have all the nutrients needed for a meal for you to have for your breakfast/lunch or dinner.
A protein powder will be there as a snack to ensure you’re hitting the correct protein levels needed daily.
Of course, you can add fruit/oats or whatever else you like to a protein powder to turn it into a meal, and you can also consume a meal powder as a snack (if bulking or to reach your daily calorific intake).
It’s important to look at the nutritional values of the powders you’re looking into to ensure you’re getting the nutrients you need.