Sequential circuits are logic circuits whose outputs not only depend on the present input but also on the past outputs. These circuits have memory elements, such as flip-flops or latches, which store and retain information about previous inputs and outputs.

Combinational Circuits:
Combinational circuits, on the other hand, are logic circuits whose outputs depend solely on the present input values. These circuits do not have any memory elements and their outputs are determined by the combination of the input values at a given instant.

Sequential Circuits:
Sequential circuits are designed to have memory elements, allowing them to store and remember past outputs. These circuits can be used to create systems that have memory and can perform tasks based on the history of inputs.

Memory Elements:
The memory elements in sequential circuits are typically flip-flops or latches. These components can store a single bit of information and have two stable states (0 and 1). They can retain their current state until they receive a clock signal or a control signal to change their state.

Flip-Flops:
Flip-flops are the most commonly used memory elements in sequential circuits. They have two stable states, which are represented by the logic levels 0 and 1. The state of a flip-flop can be changed by applying appropriate inputs and clock signals.

Latches:
Latches are another type of memory element used in sequential circuits. They can store one bit of information and have two stable states, similar to flip-flops. However, latches are level-sensitive and can change their state as long as the input conditions are met.

Dependence on Past Outputs:
The key characteristic of sequential circuits is their dependence on past outputs. The current output of a sequential circuit is influenced by the present input as well as the previous outputs. This allows these circuits to perform tasks that require memory or require the consideration of past inputs.

In conclusion, the logic circuits whose outputs depend not only on the present input but also on the past outputs are called sequential circuits. These circuits utilize memory elements like flip-flops or latches to store and remember past outputs, enabling them to perform tasks that require memory or history-dependent operations.