Explanation
References:

Policy Layers and Sub-Policies
R80 introduces the concept of layers and sub-policies, allowing you to segment your policy according to your network segments or business units/functions. In addition, you can also assign granular privileges by layer or sub-policy to distribute workload and tasks to the most qualified administrators
* With layers, the rule base is organized into a set of security rules. These set of rules or layers, are inspected in the order in which they are defined, allowing control over the rule base flow and the security functionalities that take precedence. If an "accept" action is performed across a layer, the inspection will continue to the next layer. For example, a compliance layer can be created to overlay across a cross- section of rules.
* Sub-policies are sets of rules that are created for a specific network segment, branch office or business unit, so if a rule is matched, inspection will continue through this subset of rules before it moves on to the next rule.
* Sub-policies and layers can be managed by specific administrators, according to their permissions profiles. This facilitates task delegation and workload distribution.
Reference: https://community.checkpoint.com/docs/DOC-1065

Explanation
ClusterXL has four working modes. This section briefly describes each mode and its relative advantages and disadvantages.
Load Sharing Multicast Mode
Load Sharing Unicast Mode
New High Availability Mode
High Availability Legacy Mode
References:

Configuring Interfaces
Configure the Security Gateway 80 interfaces in the Interfaces tab in the Security Gateway window.
To configure the interfaces:
1. From the Devices window, double-click the Security Gateway 80.
The Security Gateway window opens.
2. Select the Interfaces tab.
3. Select Use the following settings. The interface settings open.
4. Select the interface and click Edit.
The Edit window opens.
5. From the IP Assignment section, configure the IP address of the interface:
1. Select Static IP.
2. Enter the IP address and subnet mask for the interface.
6. In Security Zone, select Wireless, DMS, External, or Internal. Security zone is a type of zone, created by a bridge to easily create segments, while maintaining IP addresses and router configurations. Security zones let you choose if to enable or not the firewall between segments.
Reference: https://sc1.checkpoint.com/documents/R76/
CP_R76_SmartProvisioning_WebAdmin/16741.htm