Remember this first, base64 is not an encryption method nor hashing algorithm. All base64 encoded data can be reversed to original string using base64 decoding. So this base64 encode tool will help to convert string to its base64 format. Unlike hashing algorithms base64 encode will not provide a fixed length character, it purely depends on the user input data.
Base64 is a cluster of similar binary-to-text encoding schemes that represent binary data in an ascii string format by translating it into a radix-64 representation. So it is not an ascii encoding method. Base64 encoding represents a string in a binary format and converts it into simple text string.
Base64 encoding is usually used to avoid possibility of modification during data transfer from one media to another media. This can usually happens when you send directly to other systems in binary format. So it simply converts binary data to encoded using 64 character set used in base64 system
One of the disadvantage of base64 encoding, it actually increases its length.