According to Stan Carey at Sentence First:
λ♥[love] is written and sung by Christine Collins, a writer and self-described time traveller [Doctor Who fan] from the U.S. She describes it as “a convenient, terminology-dropping, non-gender-specific love song for all your linguist-seducing needs”.
You can find the lyrics in Stan's blog post, along with explanatory links ("denotation", "anaphor", "allophone", etc.). He doesn't explain the title notation λ♥[love], so I'll offer a brief note below. You can go to the Wikipedia article on the lambda calculus ("a formal system for function definition, function application and recursion") for a more complete and rigorous account.
The general idea is that if t is some expression that includes a variable x, then λx.t is a function that binds its input to the occurrence(s) of x in t. Thus λx.x is the identity function, and (λx.x)s is the identity function applied to s.
In Christine Collins' song title, the relevant term is symbolized by a letter-string ("love") demarcated by square brackets, and the variable being bound (to its putative occurence(s) in that term) is ♥.
Using a similar notation, we could write a function that adds 1 to its argument as λx[x+1].
Christine begins her song with these lines
Let me have your heart and I will give you love
The denotation of my soul is the above
So just as λx[x+1] is a function that we can define as "give me a number and I'll return that number incremented by one", so λ♥[love] is a function that we can define as "give me your heart and I'll give you love".