Under the For Sale section of the Catalog you can find four types of object currently being sold: BC (Builders Club) Objects; Limited to only BC members. LimitedU Objects; Limited to a certain amount of the object until sold out. Limited Objects; Limited to only a certain of time being sold, after that it will be no longer be available for sale.
Sponsored items were usually sold for 1 Ticket, but since the removal of Tickets , sponsor items are now free. Some sponsored items can only be obtained through promo codes for a limited time, or occasionally later put on sale (for example, the Transylvanian Hood was obtainable for a few days via the code "HOTELT2", but was later on sale for 1 tickets). Free items are some of the fastest-selling items.
Under the Public Domain section of the Catalog you can find objects being sold by ROBLOX users. You can find, buy, and favorite items being sold. There are eight categories: Heads, Faces, Gear, Accessories, T-Shirts, Shirts, Pants, Packages. All the categories display objects of that genre; e.g. Under the Accessories section you will only find accessories. You can also create your own objects and sell them under your account, giving it out to any other users.
When a player loses connection while on the catalog, a red box will appear on top of the catalog, notifying them the catalog is unavailable.
Sometimes, ROBLOX would randomly make various items that were on sale for a period of time timed, usually so ROBLOX can focus on other catalog items. Some examples include the Fallen Artemis Bow gear item being marked as timed sometime during March or April of 2016, and the Red ROBLOX Glider gear item being marked as timed during early July 2016. Some holiday-related items or items related to a special event would go on sale sometime before or during a holiday or special event and become timed, and would usually go off sale once the holiday or special event the catalog item is related to is over. An example would be the Classic ROBLOX Pumpkin Head, which is only available during the month of October and would be put off sale once Halloween ends. Some items are immediately marked as timed after they go on sale. For example, the Blue Sparkle Time Bowler was timed for one day for 5,000 ROBUX sometime during the end of June 2016. Occasionally, these items would later become limited items (usually during a sale, such as a President's Day sale, a Memorial Day sale, a Labor Day sale, or a Black Friday sale).
Until April 15, 2016, players could use the Trade Currency button to swap Tix for ROBUX. This often helped when buying ROBUX items, since it was a currency that only Builders Club members get a stipend of. When a player purchases an item, it is added to their models, allowing them to use it in the ROBLOX Studio.
There is a Commentary box down at the bottom of the purchasing page. Here players can post what you think of the object being sold. As of late May 2016, the box was removed on every single catalog item created by ROBLOX, but user-created content that have comments enabled are still visible.
When searching items, there is a "Dark" or "Light" Background button to the left. When clicked, it will change the background accordingly. Under that will be a "Hide" or "Show" Item Details button, and when clicked will also execute accordingly. If a player clicks on an item being displayed, it will show the purchasing page. Here, in the top right of the object visual, will show a box with a picture of the seller and the price. Each object has a category, which is displayed here, along with a short description of the object.
Rental items are items that have a set expiration date. Many gears do have expiration times, not limited to gears but other catalog items. Sponsored items such as the Flintstones Car and The Amazing Spider-Man are rental items. They had 4-week and 2-week rentals, respectively.
The deep catalog is the name given by many players to the strange items in the catalog. A notable item in catalog is simply named Item, which is LimitedU. Also some items known as adslkasljdfla'd and The Void Star Gift Box exist in catalog. There is also an unnamed gear item which only consists of a period in its title, which was never put on sale and is simply a blank gear item. Some players also imagine things and create creepypastas, but the actual purpose of those items is that they are test items.