What kinds of postal materials can philatelists collect besides postage stamps?

Philately is defined as the study and collection of postage stamps and various other materials related to postal delivery. Beyond postage stamps, philatelists often collect the following items:1

• Postal Stationery: This category includes items such as envelopes, wrappers, and letter sheets that are issued by postal authorities with imprinted stamps or indicia indicating prepayment of postage.1
• Postmarks: Collectors study and preserve the official markings applied to mail to cancel stamps or indicate the date and place of processing.1
• Postcards: These are frequently collected as part of broader postal history.1
• First Day Covers: These are envelopes or covers franked with a newly issued postage stamp, bearing the postmark of the first day of issue and often featuring a cachet (a decorative design) related to the stamp's subject.23
• Revenue Stamps: Some philatelists specialize in collecting stamps used to collect taxes or fees rather than for postage.1

Many collectors also focus on thematic or topical collecting, where they gather materials based on specific subjects depicted on the items, such as animals, sports, religion, or historical events.1