Base64 Encoding and Decoding

Base64 encoding or b64 encode is converting binary-text (readable text => binary => Base64 encoded text)
Base64 encoding takes 6 bits of a 8 bit char value and converts it to Base64 equivalent of it (see table for the representation in Base64 of the ascii charset).
So 2 chars needs 12 bits (1 byte + 4 bits) to encode to 1 symbol in base64
3 chars of text input needs 18 bits (2 bytes + 2 bits)
4 chars of text input needs 24 bits (3 bytes)

Base64 decoding or b64 decode means converting Base64 encoded data back to binary from which we get back the readable text .
( Base64 encoded text => binary => readable text)

Base64 scheme is used in URL encoding to escape special reserved characters for transmission over internet.
It is also useful for image, audio/video, document encoding and transmission over the network
It is more compact and a more human readable and understandable format than the binary system of 1's and 0's.
Compared to hexadecimal encoding, it encodes more chars with less bytes.
Therefore, it is considered more efficient than hexadecimal (Hexadecimal uses 8 bytes for 4 chars, Base64 uses 3 bytes for 4 chars)

Padding is done to indicate to the decoder that it is end of the stream and no additional bits for decoding.
The padding character used in Base64 is = .
The padding char is ignored and used only as an indicator
This is most useful when multiple base64 encoding content is sent
The base64 encoding takes groups of four 6 bit input (24 bits) to encode 4 chars.
When there are less than 24 bits then it uses padding char one or more of padding (=) to fill up the remaining bits to make up the 24 bit.

it contains the ascii range of characters with a-z , A-Z and 1-9 and + / and one or two = for padding.

3 bytes which represent 4 chars

6 bits

UTF-8 is the standard encoding used for encoding text. Every character in Unicode has a unique code point.
UTF-8 is a variable width encoding format.
It uses 1 byte (8 bits) to represent ascii range characters and extends to 2, 3 or 4 bytes to cover full range of charset.
UTF-8 is apt for text encoding, Base64 encoding is more suitable for binary form of data.
It is fixed length of 6 bits for a char.
It does not cover all character set like UTF-8. It's purpose is limited to data transmission without misinterpretation.

Hex is base 16 and uses range from 0-9 and A-F.
Every char is represented by 2 hexadecimal (8 bits, 2bytes).
Base64 uses base as 64 and range from 0-63.
It uses 6 bits per char instead of 8 bits and so uses 33% less size.
Hex encoding is more compact and simpler readable format.
Base64 appears more complex with its larger range and with padding chars.

Basic authentication is one of the http authentication scheme
Base64 is used to encode the user name and password while sending from client to server.
The format uses the keyword Authorization: and then followed by the word Basic and the Base64 data.
Authorization: Basic dXNlcm5hbWUvcGFzc3dvcmQ=
Base64 encoded text can be decoded and it's not secure way of transmission.

This is pertaining to email message data transmission especially attachments like images, audio, video , docs etc.
The binary form of email message / data is encoded into the plain text format using Base64 or any of other encoding algorithms and shared across email network.