> ## Documentation Index > Fetch the complete documentation index at: https://docs.lynxssp.com/llms.txt > Use this file to discover all available pages before exploring further. # Specification, Type & Category There are several levels and criteria for inventory that can be added to the Lynx SSP Platform, starting with Specification, Type, and Category. The hierarchy of these inventory levels is as follows: Hierarchy Pn ## Specification Specifications are a new classification within the Display Specification for media inventory that you must fill out to categorize media inventory based on its ad placement location. This classification aims to group ad media based on where the ad is placed and how it reaches the audience. Inventory consists of three specifications: ### Roadside Roadside is an inventory media placed along highways, main roads, and high-traffic areas, such as billboards. This media is intended to capture the attention of passing motorists and pedestrians. Roadside Pn *** ### Place Based Place-Based is an inventory media placed in a specific location with a high potential audience, such as shopping malls, airports, or train stations. This media is designed to target an audience in a specific area with a suitable campaign message. Place Based Pn *** ### Fleet Fleet is a type of moving media inventory placed on vehicles like buses, taxis, trucks, or LED cars. This media reaches audiences in various locations as the vehicles move. Fleet Pn *** ## Type & Category There are two types of inventory that can be added to the Lynx SSP: DOOH (Digital-Out-of-Home) and OOH (Out-of-Home) Inventory. Here are the definitions for each type: ### **DOOH (Digital-Out-of-Home)** This is a type of digital outdoor media that uses electronic screens to display advertisements or content. Examples include digital billboards (known as videotron), mobile LEDs, etc. DOOH allows for content to be managed in a real-time and flexible manner. *** ### **OOH (Out-of-Home)** This is a conventional, static form of outdoor media. Examples include billboards, banners, posters, and other printed outdoor media. OOH displays advertising materials in a fixed, printed visual format.