Bitcoin installation
The Bitcoin Core client can be installed from https://bitcoin.org/en/download. This is available for different architectures and platforms ranging from x86 Windows to ARM Linux, as shown in the following screenshot:

Download Bitcoin Core
Types of Bitcoin Core clients
Let's explore the different types of Bitcoin Core clients.
Bitcoind
This is the core client software that can be run as a daemon, and it provides the JSON RPC interface.
Bitcoin-cli
This is the command line feature-rich tool to interact with the daemon; the daemon then interacts with the blockchain and performs various functions. Bitcoin-cli calls only JSON-RPC functions and does not perform any actions on its own on the blockchain.
Bitcoin-qt
This is the Bitcoin Core client GUI. When the wallet software starts up first, it verifies the blocks on the disk and then starts up and shows the following GUI:

Bitcoin Core QT client, just after installation, showing that blockchain is not in sync
The verification process is...