This verse is part of the story of Joseph in Genesis, where he is interpreting Pharaoh's dreams. It's crucial to understand it in the context of the entire dream sequence. Here's what it means:

"He slept and dreamed a second time:" Pharaoh had already had one dream (of seven healthy and seven skinny cows). This is his second, related dream. The repetition emphasizes the importance of the dreams and suggests a unified meaning.

"and behold, seven heads of grain came up on one stalk, healthy and good." This is the core image of the dream. Let's break it down:
Seven heads of grain: Represents a plentiful harvest, a time of abundance. The "seven" is significant and links directly to the seven cows in the previous dream.
Came up on one stalk: This emphasizes a single, strong source. It suggests the abundance is coming from a unified foundation.
Healthy and good: Reinforces the idea of thriving and prosperity. This signifies a period of exceptional harvests.

Symbolic Meaning (within the story):

In the context of the story, this dream, along with the dream of the cows, is a prophecy. It represents seven years of abundant harvests in Egypt. This is a foreshadowing of the events to come and the central problem Joseph will soon be asked to solve.

How it Relates to the First Dream:

The dream of the seven healthy heads of grain is directly related to the dream of the seven healthy cows. Together, they paint a picture of seven years of prosperity. The interpretation, which Joseph will provide, is that these seven years will be followed by seven years of famine.

In short, the verse describes a vision of extraordinary agricultural abundance, predicting a coming period of great harvest and prosperity for Egypt.