CSS Grid and Flexbox are two powerful layout systems in CSS, each designed to handle different kinds of layout needs. Here's a brief overview of each:

CSS Grid

CSS Grid is a two-dimensional layout system, meaning it can handle both rows and columns. It's ideal for more complex, grid-based layouts.

Key Features:

• Two-Dimensional Layout: CSS Grid works on both axes (horizontal and vertical), making it perfect for creating complex layouts where items are aligned in both rows and columns.
• Explicit Grid: You can define the grid structure explicitly using grid-template-rows, grid-template-columns, and grid-template-areas.
• Placement Control: Items can be placed precisely using grid line numbers or named areas, offering fine control over where items are placed.
• Gaps: The grid-gap property (or gap in newer CSS) allows for easy spacing between grid items.
• Responsive Design: CSS Grid can easily adapt to responsive design, with different grid layouts for different screen sizes.

Example:

.container {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: auto;
  gap: 10px;
}

.item1 {
  grid-column: 1 / 3;
  grid-row: 1;
}

Flexbox

Flexbox (Flexible Box Layout) is a one-dimensional layout system, perfect for layouts in a single direction (either a row or a column).

Key Features:

• One-Dimensional Layout: Flexbox is designed for laying out items in a single direction, either horizontally or vertically.
• Flex Containers and Items: A flex container's children become flex items that can be aligned, spaced, and ordered.
• Alignment and Justification: Flexbox provides powerful alignment options such as justify-content, align-items, and align-content.
• Flexible Sizing: Flex items can grow, shrink, or stay fixed based on the available space, using properties like flex-grow, flex-shrink, and flex-basis.
• Order Property: You can change the visual order of items without altering the HTML using the order property.

Example:

.container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.item1 {
  flex-grow: 2;
}

.item2 {
  flex-grow: 1;
}

When to Use CSS Grid vs. Flexbox

• Use CSS Grid: When you need a complex layout with both rows and columns, such as a grid of cards, a dashboard, or a multi-column web page.
• Use Flexbox: When you need a simpler layout in a single direction, such as a navigation bar, a set of buttons, or aligning items in a single row or column.

Both systems can be used together for different parts of a web page to create complex and responsive layouts.