Line-intensity mapping (LIM) is an emerging approach to survey the Universe, using relatively low-aperture instruments to scan large portions of the sky and collect the total spectral-line emission from galaxies and the intergalactic medium. Mapping the intensity fluctuations of an array of lines offers a unique opportunity to probe redshifts well beyond the reach of other cosmological observations, access regimes that cannot be explored otherwise, and exploit the enormous potential of cross-correlations with other measurements. This promises to deepen our understanding of various questions related to galaxy formation and evolution, cosmology, and fundamental physics. Here, we focus on lines ranging from microwave to optical frequencies, the emission of which is related to star formation in galaxies across cosmic history. Over the next decade, LIM will transition from a pathfinder era of first detections to an early-science era where data from more than a dozen missions will be harvested to yield new insights and discoveries. This review discusses the primary target lines for these missions, describes the different approaches to modeling their intensities and fluctuations, surveys the scientific prospects of their measurement, presents the formalism behind the statistical methods to analyze the data, and motivates the opportunities for synergy with other observables. Our goal is to provide a pedagogical introduction to the field for non-experts, as well as to serve as a comprehensive reference for specialists.

线强度测绘（LIM）是一种新兴的宇宙调查方法，它使用相对低孔径的仪器扫描大部分天空并收集来自星系和星系间介质的总谱线发射。绘制一系列线的强度波动提供了一个独特的机会来探测远远超出其他宇宙学观测范围的红移，访问无法以其他方式探索的机制，并利用与其他测量的互相关的巨大潜力。这有望加深我们对与星系形成和演化、宇宙学和基础物理学相关的各种问题的理解。在这里，我们关注从微波到光学频率的谱线，其发射与整个宇宙历史中星系中的恒星形成有关。在接下来的十年中，LIM将从首次探测的探路者时代过渡到早期科学时代，在这个时代，来自十多项任务的数据将被收集以产生新的见解和发现。这篇评论讨论了这些任务的主要目标线，描述了对其强度和波动进行建模的不同方法，调查了其测量的科学前景，介绍了分析数据的统计方法背后的形式主义，并激发了与其他任务协同的机会可观察到的。我们的目标是为非专家提供该领域的教学介绍，并为专家提供全面的参考。