# not the most efficient way,
# but you get the idea.

str = "meow"

# convert string to binary
bin = str.bytes.map{|d| d.to_s(2)}.map{|b| b.rjust(8, '0')}.join
puts bin

# and convert it back to a string
str = bin.scan(/.{8}/).map{|m| m.to_i(2)}.map{|n| n.chr}.join
puts str

# and here come the explanations
bin = str.
    bytes. # split the string into it's bytes
    map{|d| # iterate over the bytes
        d.to_s(2)}. # turn each into string in base 2
        map{|b| # iterate over the strings
            b.rjust(8, '0')}. # pad each to be 8 characters wide (fill with zeros on right side)
                join # piece them together as string

str = bin.
    scan(/.{8}/). # split the string into groups of 8 characters (.{8} matches 8 characters)
    map{|m|         # iterate over the groups
        m.to_i(2)}. # turn each to an int, interpreting it to be in base 2
        map{|n|     # for each int
            n.chr}. # turn it into a character
                join # join the resulting characters into a string