Breadth First Search (BFS) algorithm can be used to find all the connected components in an undirected graph.

Explanation:
- BFS is a graph traversal algorithm that explores all the vertices of a graph in breadth-first order.
- It starts at a given source vertex and explores all of its neighbors before moving on to the next level of neighbors.
- By using BFS, we can visit all the vertices that are reachable from a given source vertex.
- In an undirected graph, a connected component is a subgraph in which every pair of vertices is connected by a path, and there is no path between any vertex in the subgraph and any vertex outside the subgraph.
- By running BFS on each vertex of the graph, we can find all the connected components.

Steps to find connected components using BFS:
1. Initialize an empty list to store the connected components.
2. Initialize a boolean array to keep track of visited vertices.
3. For each vertex in the graph, if it is not visited, perform the following steps:
- Create a new empty list to store the current connected component.
- Enqueue the current vertex into a queue.
- Mark the current vertex as visited.
- While the queue is not empty, do the following:
- Dequeue a vertex from the queue.
- Add the dequeued vertex to the current connected component list.
- For each neighbor of the dequeued vertex, if it is not visited, enqueue it into the queue and mark it as visited.
- Add the current connected component list to the list of connected components.
4. Return the list of connected components.

Example:
Consider the following undirected graph:

A---B E
| |
C---D

- The connected components in this graph are {A, B, C, D} and {E}.
- Starting with vertex A, BFS will visit all the vertices in the first connected component.
- Then, starting with vertex E, BFS will visit the second connected component.
- The final result will be [{A, B, C, D}, {E}].

Conclusion:
By using Breadth First Search (BFS) algorithm, we can find all the connected components in an undirected graph. It explores all the vertices in breadth-first order, allowing us to identify which vertices are reachable from a given source vertex and form the connected components.