A patent license is a contract between two parties, a licensor who owns a patent right and a licensee who wants to practice what the patent claims. If the licensee is a business, it is possible but would be uncommon to pay for a license without knowing what patents it covers. Contracts with businesses are not usually published, so it would be uncommon for you to know what patents are covered by somebody else's license agreement. When an end-user buys a product or service, it comes with an implied license from the seller for any patents that cover the product or service.
If somebody says that they own a patent that covers a technology, whether it is licensed to others probably shouldn't make much difference to you. If you would like to know what patents are owned by a specific owner ("assignee"), you can do a worldwide search on Google Patents or Espacenet by filtering results for the assignee. Be aware that the spellings of company names are inconsistent, so be sure to search with and without "inc", ", inc", and the names of parent companies or subsidiaries. Theoretically, a patent can be sold without recording a new assignment. however, most sales are publicly recorded, at least for US patents.
If you want to know what technologies are covered by patents, you can use those search engines and enter keywords that are related to the technology.
Different countries have different laws about patent marking. Under US law, 35 U.S. Code § 287 says that a patent owner can only collect money for your infringing activity ("damages") once that have put you on notice of your infringement. That can come from them, for example, sending you a letter or by marking their patent number(s) on the product. Some products are small and implement technologies covered by many patents. For such products, a URL to a web page listing patents covering the product is appropriate notice. However, you can be held liable for any infringmeent of patents that claim a method, even if the patent owner provides no marking.