"The Tyger" and "The Lamb" are both poems from Blake's work "Songs of Innocence and Experience". The title of the volume itself gives you a hint about their meaning. In "The Tyger", the narrator asks "What immortal hand or eye could frame thy fearful symmetry?". The speaker in "The Lamb" asks, "Little lamb who made thee?". Both speakers are asking who created these creatures. Blake is asking how God could have created both the monstrous tyger and the innocent lamb? How do we as human beings reconcile the existence of both good and evil?
Both "The Tyger" and "The Lamb" were published in Blake's book Songs of Innocence and Experience. Although the poems are both deceptively simple, they are actually important examples of Blake's unique religious beliefs, which incorporate certain Christian elements as well as many ideas Blake himself invented.
Both poems ask about the problem of creation. Christians of Blake's period tended to believe literally in the account found in Genesis of God's creation of the world and the animals that populate it. Blake sees that the world is complex, including both good and evil, fragility and strength, and gentleness and ferocity. Thus his two questions ask how a single Creator working over a short period of time could have created such diversity and why He might have done so.
Both of the questions, "What immortal hand or eye could frame thy fearful symmetry?" ("The Tyger") and "Little lamb who made thee?" ("The Lamb") are speculating about what we can understand of the Creator of our world by observing His creations.