OK. Common examples of rent-seeking would include:
The NFA previously required payment of a $200 fee for a 'stamp' or something, so that you would be permitted to purchase a suppressor, or other restricted firearm accessories. Adding absolutely NO value to the transaction, other than registration, which would be the second criteria to be considered as a 'rent-seeker'.
Many states permit reciprocal privileges for certain trades and such, those in the cosmetology and similar fields, but they require a license fee anyways. This is to me 75% rent-seeking, they don't even test you, they should just accept the other states' licenses and just make them renew at their previous state. Which would then trigger a real licensing event, but we digress...
Many other professions in America and elsewhere are required to be licensed, pay fees, and not for any purpose than to share in the revenue.
From Wikipedia: "Rent-seeking is the practice of individuals or businesses trying to gain economic benefits through manipulation of public policy or economic conditions, rather than through productive activities.". A definition, but one I think is somewhat limited. But based, quoting, on "Adam Smith's division of incomes into profit, wage, and economic rent. The origin of the term refers to gaining control of land or other natural resources."
This is where the depiction of landlords as rent-0seekers comes from, their ownership of property and deriving revenue from that. In truth, this more accurately refers to the Middle Ages and other eras where the local warlord (etc.) would purport to provide protection and other benefits to the surrounding villagers and farmers in exchange for a 'tax', a share of their goods, crops, revenue. This ultimately, in England, became the landed gentry system, with the good results of the Magna Carta, and the bad effects Adam Smith documented as described above, somewhat.
Regulatory capture is a more contemporary example, and along with so many other effects, such as failed regulation and even damaging practices... Even more harm.
Landlords that offer their property for occupancy, for a fee, collect rent, but offer the value and utility of the space. Not rent-seeking in the economics understanding. Collecting a fee to permit you to occupy a seat in a stadium and enjoy viewing a movie is also not that form of 'rent-seeking', though it resembles landlord activity, differing in the space made available, the duration of the lease, and not merely an enclosed space suitable for habitation or business, but the provision of entertainment...
Demonization of landlords in the root example here was based on the allegation that increases in property value within a neighborhood being 'gentrified', and resulting in those property value increases, should be shared with tenants in commercial property, despite those tenants, presumably because they should be renumerated for their contribution to the overall improvements and such. This ignores that likely reality that they both are in business ONLY because of the local economic improvements, and also that their success of failure is not entirely dependent on the landlord, beyond their landlord providing suitable premises.
But demonization of successful private enterprises is a basic tenant of Marxism, which is getting popular in the US. That's an entirely different discussion etc.