Splunk products

There are several types and licensing models of Splunk available to suit the needs of its customer base.

Splunk Enterprise is designed for on-premise deployments; it can be scaled to support an unlimited number of users and ingestion volumes by adding the necessary number and types of Splunk functional software components (indexers and search heads) on customer-supplied servers. The cost of a Splunk Enterprise license is based on daily ingestion volume. A wide range of applications for Splunk Enterprise, written by both Splunk and the user community, that add value to the product are available for free from the Splunkbase website. Splunk also sells several sophisticated premium solution applications such as IT Service Intelligence, Enterprise Security, and User Behavior Analytics on an individual license basis, and a Machine Learning Toolkit is available for free from Splunkbase if you want to roll out your own ML solutions.

Splunk Cloud is a cloud-based software as a service (SaaS) version of Splunk Enterprise; it is also licensed based on daily ingestion volume, and offers all the functionality of the on-premise Splunk Enterprise product. The core Splunk infrastructure is provided and managed by Splunk, while data inputs, approved apps, reports, dashboards, alerts, and so on are managed by the customer.

Splunk Light is designed to be a small-scale solution. It allows up to 20 GB/day of ingestion volume, five users, and reports/dashboards/alerts, but does not provide support for distributed deployments, Splunkbase or premium solution apps (except for an app for Amazon Web Services (AWS)), and several other limitations.

Splunk Free is a free version of the core Splunk Enterprise product that has limits on users (one user), ingestion volume (500 MB/day), and other features; also, it cannot be used for a deployed/clustered configuration. 

You can compare the available features of each product here: https://www.splunk.com/en_us/software/features-comparison-chart.html.