by and by vs later

by and by

• After a short time. 

• After an indefinite period. 

• Heaven; the hereafter. Usually preceded with "the sweet." 

later

• At some unspecified time in the future. 

• Afterward in time (used with than when comparing with another time). 

• See you later; goodbye. 

• At some time in the future. 

• Coming afterward in distance (following an antecedent distance as embedded within an adverbial phrase) 

• Coming afterward in time (used with than when comparing with another time).