> For the complete documentation index, see [llms.txt](https://deeplearning4j.konduit.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts.md).

# Core Concepts

- [Ecosystem Overview](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts/ecosystem-overview.md): Overview of the Eclipse Deeplearning4j ecosystem — ND4J, DL4J, DataVec, SameDiff, Python4J, and OmniHub
- [Tensors and NDArrays](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts/tensors-and-ndarrays.md): INDArray fundamentals — shape, rank, stride, DataType, creating arrays, views vs copies, and off-heap memory in ND4J
- [Data Pipelines](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts/data-pipelines.md): Loading, transforming, and feeding data for training — RecordReader, DataSetIterator, normalization, and mini-batching
- [Neural Network Fundamentals](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts/neural-net-fundamentals.md): Layers, activation functions, loss functions, weight initialization, and regularization in Deeplearning4j
- [The Training Loop](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts/training-loop.md): Building, configuring, and training neural networks — NeuralNetConfiguration, updaters, fit(), listeners, and ComputationGraph
- [Evaluation](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts/evaluation.md): Evaluating model performance — classification metrics, ROC curves, regression metrics, and evaluation during training
- [Memory and Workspaces](https://deeplearning4j.konduit.ai/en-1.0.0-rewrite/core-concepts/memory-and-workspaces.md): Off-heap memory management, JVM configuration, workspace modes, and troubleshooting memory issues in ND4J and DL4J